The present invention relates to high temperature superconductors.
Recently, there has been much work done on the development of high temperature superconductors. Recent developments have indicated that certain combinations of elements are superconducting. However, these compositions typically do not maintain their superconductive attributes at temperatures that exceed approximately 90 K. For example, recently, much work has centered on the use of ternary oxides containing rare earth elements, barium, and copper for superconductivity above the temperature of liquid nitrogen. But, these systems have limited transition temperatures, at or below 93 K, and thus their applications are limited.
U.S. patent application Ser. Nos. 082,222, 089,067, and 144,114, filed on Aug. 6, 1987, Aug. 25, 1987, and Jan. 15, 1988, respectively, in the name of the inventors of the present invention disclose superconductor systems. U.S. patent application Ser. No. 089,067 discloses, in part, a superconductor based on a R-Ba-Cu-O wherein R is chosen from the group of rare earth metals excluding praseodymium, cerium, and terbium. U.S. patent application Ser. No. 082,222 discloses, in part, a superconductor based on a Tb-R-Ba-Cu-O system wherein R is chosen from the group of rare earth metals excluding praseodymium, cerium, and terbium. U.S. patent application Ser. No. 144,114 discloses, in part, a superconductor based on a TlBaCuO system.
Although superconductors prepared pursuant to the systems disclosed in the above-identified patent applications have produced "high temperature" superconductors and yielded optimistic test results, superconductors prepared pursuant to the present invention have yielded higher transition temperatures. Indeed, based on the knowledge of the inventors, superconductors produced pursuant to the present invention have yielded the highest transition temperatures to date for any superconductor.
A superconductor with a higher transition temperature would be desirable for many reasons. Such a superconductor would: (1) facilitate the discovery of the correct theory on oxide superconductivity; (2) provide a framework for the search of higher temperature, even room temperature superconductors; (3) allow superconducting components to operate at higher temperatures with lower cost; and (4) provide low cost processing and manufacturability.
Furthermore, many of the superconductor compositions that have been proposed to date are based on rare earth metals. Due to the short supply and cost of these rare earth metals, the compositions constructed therefrom can be quite expensive.
Accordingly, there is a need for improved superconductors with higher transition temperatures.